Ascites & SBP

Ascites is one of the most common complications of cirrhosis seen on medical wards in the NHS.
Spontaneous bacterial peritonitis (SBP) is a life-threatening complication that can be subtle and easily missed.

This guide focuses on what doctors actually need to do on the ward and on-call.

What is ascites?

Ascites is the accumulation of fluid in the peritoneal cavity, most commonly due to portal hypertension in cirrhosis.

SBP is infection of ascitic fluid without an obvious intra-abdominal source.

How does it present?

Ascites:

  • Abdominal distension
  • Discomfort
  • Early satiety
  • Shortness of breath
  • Peripheral oedema

SBP (often subtle):

  • Fever
  • Abdominal pain or tenderness
  • Worsening ascites
  • Confusion / encephalopathy
  • AKI
  • General deterioration

Important:

SBP does not always present with dramatic abdominal pain.
Any unwell cirrhotic with ascites → consider SBP until proven otherwise.

Common causes (think practically)

Ascites is most commonly due to:

  • Cirrhosis
  • Alcohol-related liver disease
  • MASLD / NAFLD

Less commonly:

  • Malignancy
  • Cardiac failure
  • TB peritonitis

SBP occurs in patients with:

  • Known cirrhosis and ascites
  • Low protein ascites
  • Previous SBP
  • Recent GI bleed

On the ward, always ask

Has this patient had an ascitic tap?

If not, why not?

Any patient with:

  • Cirrhosis + ascites + admission to hospital
    should usually have a diagnostic ascitic tap, even if they look well.

First priority = Don’t miss SBP

SBP kills because it is missed, not because it is untreatable.

Think SBP if:

  • Cirrhotic patient deteriorates
  • New confusion
  • Fever
  • AKI
  • Rising inflammatory markers
  • No clear source of sepsis

Immediate management on the ward (what juniors should actually do)

If reviewing a patient with ascites:

Do early:

  • Full A–E assessment
  • Bloods: FBC, U&E, LFTs, INR, CRP
  • Blood cultures if infection suspected
  • Perform ascitic tap (or escalate to someone who can)
  • Send ascitic fluid for:
    • Cell count
    • Culture
    • Albumin

SBP diagnosis:

  • Neutrophils ≥250/mm³ in ascitic fluid = SBP (treat immediately)

Do not wait for cultures.

If SBP suspected or confirmed

Start:

  • IV antibiotics (e.g. ceftriaxone as per local guideline)
  • IV albumin (reduces risk of renal failure)
  • Monitor renal function closely
  • Early gastro involvement

SBP is a medical emergency.

When to escalate

Escalate urgently if:

  • Hypotension
  • AKI
  • Encephalopathy
  • Rising lactate
  • NEWS ≥5
  • Concerned nursing staff

These patients may require:

  • HDU/ICU
  • Vasopressors
  • Renal support

Common mistakes juniors make

  • Not performing ascitic tap
  • Waiting for imaging before tapping
  • Assuming ascites = “chronic problem”
  • Missing SBP in confused patients
  • Delayed antibiotics
  • Forgetting albumin

Take-home concept

In cirrhosis, ascites is common — but SBP is deadly.
If a patient with ascites is unwell, tap early, treat early, and escalate early.